Procedure for producing textiles resistant to chemical warfare liquids



3,054,695 PROCEDURE FOR PRGDUCING TEXTHJE RESET- ANT T CHEMICAL WARFARELlQUlD Leopold Loeb, Louisville, Ky., and Robert L. Clayton, J12, NewOrleans, Stanley P. Kolturn, Metairie, Frederick 5. "Philips, NewGil-leans, Leon Segal, Metairie, and Kazuo H. Tahernura, New Orleans,La, assignors to the United States of America as represented by thedecretary of the Army No Drawing. Filed June 24, 1957, Ser. No. 667,7175 Claims. (Cl. 117-72) (Granted under Title 35, US. Code (E52), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment to us of any royalty thereon.

This invention relates to a process of impregnating textile materialswith a composite material which renders them highly resistant to wettingor penetration by chemical Warfare liquids without undesirably alteringtheir hand, feel, or air permeability.

Copending patent application Serial No. 667,719, file'd on even date,describes surface coatings which are resistant to chemical warfareliquids. The present invention provides an improved process of formingsuch surface coatings on the fibers of a textile material.

Heretofore numerous compositions and treatments for coating the surfacesof textile materials and other permeable materials, to render thematerials impermeable to water and similar polar liquids, have beendeveloped. Some of these treatments render the treated materials morepermeable to organic solvent soluble materials such as oil and the like,and others render the treated materials impermeable toboth water andoil. However, the more penetrating chemical warfare liquids have acapability of wetting and penetrating that is many times greater thanthat of either water or oil. Materials capable of resisting penetrationby water and oil are often almost instantaneously penetrated by a liquidsuch as the warfare liquid designated as GB by the Army Chemical Corpsi.e. isopropyl methylphosphonofluoridate. The chemical warfare liquidsare polar liquids having a low surface tension. They penetrate a clothcomposed of a cellulosic textile material in a fraction of a secondregardless of the construction or weave of the cloth.

The terms penetration time and wetting time as used in thisspecification have the following meanings. Penetration time is the timerequired for the underside of the fabric to show the first traces ofpenetration by a drop of liquid placed on its upper side. Wetting timeis the time required for a drop of the liquid placed upon the fabric todissipate, i.e., to lose its identity as a drop.

When the surface coatings described in the abovementioned copendingapplication are formed on the surfaces of the fibers of a textilematerial, the textile materials are generally resistant to Wetting andpenetration by liquid GB for at least about 100 seconds, and may beresistant for many hours. Those surface coatings comprise asubstantially homogeneous surface coating consisting essentially of acertain type of polymer to which is bonded a Werner-type chromi-nuclearcomplex in which the acido groups consist essentially ofperfluoroalkanoyl groups con- 3,054,695 Patented Sept. 18, 1962 tainingat least six carbon atoms. Although those surface coatings can be formedon the surfaces of textile fibers by a basically simple processrequiring only two steps and a minimum of control, slight variations inthe process of forming them may produce rather widely varying results,and some of the essential reactants have a relatively short working lifein the form in which they can be employed.

A primary object of this invention is to provide a substantiallyfoolproof process, adapted for field or plant use, for impregnating atextile fabric with a material that converts the fabric to one whichexhibits properties such as hand, feel, air permeability and the likewhich are substantially as desirable as those of the untreated fabricand will resist wetting and penetration by even the highly active liquidGB for at least about minutes. Another object is to provide a process ofbonding Werner-type chromi-nuclear complexes to acid sensitive materialswithout causing acid induced degradation. A further object is to providea process of bonding Wernontype chromi-nuolear complexes in which theacido groups consist essentially of periiuoroalkanoyl' groups containingat least six carbon atoms to certain polymeric surface coatings by abonding process: that enhances the resistance of the resulting compositesurface and coating to wetting by polar or non-polar liquids.

In general, in accordance with the present invention, a textile materialis rendered highly resistant to wetting and penetration by liquidchemical warfare agents by: impregnating the textile with an inertvolatile liquid containing a polymer, of the group consisting ofpolymethylacrylate, polyethylacrylate, polyvinyl-acetate, and copolymersof acrylonitrile and butadiene containing from about 30 to 60 weightpercent of acrylonitrile, to a dry pick-up of from about 25 to 50 Weightpercent; drying the impregnated textile at a temperature of from about20 to 30 centigrade; immersing the dry impregnated textile in andsubstantially immediately removing it from contact with a liquidcomposition, which is maintained at a temperature between its freezingpoint and about 5 C., and which consists essentially of water, fromabout 0.4 to 3.3 weight percent of a water soluble alleanol, fromabout0.2 to 1.5 weight percent of a Werner-typcchromi-nuclear complex inwhich the acido groups consist essentially of perfluoroalk-anoyl groupscontaining from about 6 to 18 carbon atoms, and suflicient water solublenitrogen-base to produce a pH of from about 4.8 to 5.5 (substantiallyimmediately); freeing the wet textile of drops of the liquid; and dryingthe wet textile at a temperature of from about to C. for from about 30to 90 minutes.

When a textile material is treated in accordance with the presentinvention the physical structure of the composite material with whichthe textile is impregnated appears to enhance the capacity of thetreated textile to -1 esist wetting and penetration by chemical warfareliquids. While this invention is not premised upon any particular theoryor postulated mechanism, it appears that the above combination of stepsresults in: (1) the formation of a substantially homogeneous layer of apolymeric film which surrounds and draws together at least some bundlesof fibers; and (2) the bonding to that film of a substantiallymonomo-lecular layer of uniformly distributed Werner-type chromi-nuclearcomplexes arranged so that their perfluoroalkanoyl acido groups extendto form an outer surface layer consisting essentially of chains ofcarbon atoms surrounded by fluorine atoms. Cotton sateen treated in thismanner usually resists wetting and penetration by liquid GB for at leastabout 1000 seconds and usually exhibits an air permeability equal to orgreater than that of the untreated sateen.

Substantially any textile material composed of vegetable, animal,synthetic, or glass fibers can be employed. The employment of fabricscomposed essentially of cellulosic textile fibers is preferred. Theinvention is especially adapted for the treatment of cotton clothingfabrics such as cotton sateen and the like.

The inert volatile liquids containing the polymer can be aqueousdispersions or organic solvent solutions of the specified polymers. Theliquids can contain widely varying amounts of polymers. The dispersionsor solutions can contain the amounts and types of emulsifying, wetting,and/or dispersing agents that are usually employed in polymercompositions adapted for the production of surface coatings. Thepolymers can vary widely in molecular Weight or degree ofpolymerization. The specified proportion of polymer can be applied tothe textile in one or a plurality of steps. Illustrative examples ofsuitable aqueous dispersions which are commercially available includethe film-forming dispersions of polyethylacrylate, copolymers ofacrylonitrile and butadiene or polyvinylacetate, which are availableunder the trade names Hycars, Polycos, Rhoplex, Darex, Vinylitedispersions, and Chemigum latices. Suitable organic solvent solutionsinclude solutions of the polymers in the lower alcohols such as methyl,ethyl, and the like alcohols, the lower ketones such as acetone, methylethyl ketone, the varnish solvents and the like organic solvents.

The textile materials can be impregnated with the polymer by means ofthe usual procedures and apparatus for the liquid impregnation oftextile materials; employing padders, centrifuges, squeeze rolls, andthe like. In the field, the impregnation can be accomplished by a simplehand dipping and squeezing employing a dispersion concentration and asqueezing procedure found by experience to produce the proper polymerpick-u The impregnation of the textile materials to a dry pick-up ofresin of from about 25 to 50 weight percent is preferred. Theimpregnation can be accomplished by one or a plurality of steps. Theresin-impregnated textiles can be dried by means of the usual proceduresand apparatus for the drying of textile materials, employingtemperatures between about to 30 centigrade. In the field, theimpregnated textiles can be dried by simply hanging them up in arelatively dry atmosphere.

Werner-type chromi-nuclear complexes in which the acido groups consistessentially of perfluoroalkanoyl groups containing at least six carbonatoms are known compounds. Processes of producing them and bonding themto the surface of a wide variety of materials are described in BritishPatent No. 712,784, published July 28, 1954. These complexes are alsoperfluoroalkanoyl analogs of the complexes described in U.S. PatentsNos. 2,373,040, and 2,544,666. They can be produced and applied byprocedures analogous to the procedures described in the latter patents.In general, the perfluoroalkanoyl chromi-nuclear complexes can beprepared by effecting contact in solution between the perfluoroalkanoic'acid and a basic trivalent chromium salt of a monobasic acid, whichsalt has a basicity of not more than about 50 percent. They can bebonded to the surfaces of materials simply by forming a film of a liquidcontaining them on the material. The complexes can be dissolved inorganic solvents such as isopropanol and the like alcohols. Illustrativeexamples of acids suitable for employment as the acido groups of thecomplexes include: perfiuorohexanoic, perfluorooctanoic,perfluorodecanoic, perfluorooctadecanoic and the like acids. Thecomplexes in which the acido groups consist essentially ofperfiuoroalkanoyl groups containing from about 8 to 10 carbon atoms arepreferred.

The usual compositions for bonding of Werner-type chromi-nuclearcomplexes consist essentially of rather strongly acidic solutions of thecomplexes dissolved in a water-diluted organic solvent. Such solutionsusually have a pH of from about 1 to 4. Usually, if the pH of such asolution is increased, the complex soon begins to precipitate. Yet, ifan acid sensitive material such as a cellulosic textile is contactedwith a solution having a pH as low as about 4.0, the textile undergoesnoticeable acid degradation during subsequent curing.

We have found that, if a Werner-type chromi-nuclear complex is dissolvedin a Water soluble alkanol, and the alkanol solution is cooled, dilutedand partially neutralized, to form a solution which, (a) is maintainedat a temperature between its freezing point and about 5 C., and (11)consists essentially of water, from about 0.4 to 2.0% by weight of watersoluble alkanol, from about 0.2 to 1.0% by Weight of Werner-typechromi-nuclear complex and enough water soluble nitrogen-base to producea pH of from about 4.8 to 5.5; the solution comprises a compositionwhich is uniquely adapted for bonding the complexes to acid sensitivematerials. The Werner-type complexes can be those is which the acidogroups consist essentially of the acyl groups of substantially any monovalent carboxylic acid. In contrast to the previously knowncompositions, these complex-applying compositions are characterized byan acidity not much stronger than that of distilled Water, and a workinglife of at least 24 hours. In the case of the complexes of theperfluoroalkanoic acids, the use of these complex-applying compositionsin the treatment of textile fabrics has the unobvious advantage that inaddition to avoiding acidinduced degradation, the liquid repellency isenhanced.

.The same type and amount of complex applied by means of thesecomplex-applying solutions, gives an appreciably greater resistancetoward liquid GB and the other chemical warfare liquids than thatobtained by applying the complex by means of the previously knowncompositions, or at room temperature. Illustrative examples ofwatersoluble alcohols suitable for use in these complex-applyingcompositions include methyl, ethyl, propyl, isopropyl, isobutyl, and thelike alcohols. Illustrative examples of water-soluble bases suitable foremployment in these complex-applying compositions include ammonia,monoamines such as ethylamine, polyamines such as hexamethylenetetramine, and the like. The use of isopropanol as the solvent andhexamethylene tetramine as the base, is preferred. Thesecomplex-applying compositions can be formed by cooling, diluting, andneutralizing, in the above described manner, the perfluorooctanoicWerner-type chromi-nuclear complexes dissolved to about 30 weightpercent complex in isopropanol that are commercially available under thetrade name FO-804.

The dried resin-impregnated textile material can be immersed in andsubstantially immediately removed from the chromi-nuclear complexcontaining liquid by means of the usual procedures and apparatus for soimmersing a textile material in a liquid; using padders, squeeze rolls,centrifuges, and the like adjusted to quickly free the wet textile ofliquid. In the field this operation can be accomplished by a simple handdipping and shaking. The treated textiles can be air dried by means ofthe usual procedures and apparatus for drying textile materials. Thetreated textiles are preferably dried by heating them at from about toC. for from about 30 to 90 minutes.

The following examples are illustrative of the details of at least onemethod of practicing the invention.

Example 1 Swatches of 8.5 oz. carded cotton sateen were impregnated inan aqueous dispersion of a commercially available polyethyl acrylate(Hycar 4501) containing 25% total solids. The impregnated swatches werepadded to give 100% wet pick-up and allowed to air dry at roomtemperature for 6 days. The impregnated sateen was then briefly waterwashed and allowed to redry. The perfluorooctanoic acid chromi-nuclearcomplex used for treating the impregnated sateen was prepared asfollows: 2.5 grams of a commercially available isopropanol solution(PC-804) containing 30% of the solid complex was diluted with 95 gramsof distilled water previously cooled to 5 C. The diluted solution of thecomplex was partially neutralized by the adidtion of 2.5 grams of asolution of hexamethylene tetramine. The final solution, maintained at 5C., had a solids content of 0.75% and a pH of 5 .0.

In order to demonstrate the stability of the cooled chromi-nuclearcomplex solution, swatches of the impregnated sateen, having a resin drypick-up of 24.8%, were treated in this solution at hourly intervals overa 7 hour period. The treatment consisted of briefly immersing theimpregnated sateen in the cooled complex solution and immediatelyfreeing the sateen of excess liquid. The fabric was then cured for onehour at a temperature of 105 C., after which it was briefly washed witha warmed, dilute solution of a synthetic detergent, given a water rinse,then air dried.

Times required for the penetration and wetting of the treated sateenwith stabilized liquid GB ranged from 700-2500, and 6000 to 26,000seconds, respectively. The cooled complex solution appeared to becompletely stable toward precipitation during the 7-hour period and therepellency of the treated sateen was independent of the age of thechromi-nuclear complex treating solution.

The treated sateen has a good hand, is not stiff or boardy, and has airpermeability equivalent to that of the untreated sateen.

Example 2 Swatches of impregnated sateen containing 24.8%polyethylacrylate (Hycar 4501) were briefly immersed in a cooledsolution (4 C.) of the chromi-nuclear complex (PG-804) containing 0.4%solid complex and neutralized with 10% hexamethylene tetramine (HMTA) toa pH of 5.05. After treatment of the first swatch above, the solutionwas stored for 24 hours at 4 C. and then employed for the treatment of asecond swatch of the impregnated sateen. After immersion the treatedswatches were processed exactly as described in Example 1. Therepellencies of the swatches were evaluated with stabilized BG. Thefirst swatch exhibited penetration and wetting times of 2900 and 29,000seconds, respectively; where as the swatch treated with the solutionaged 24 hours gave values of 2,200 and 10,000 seconds, respectively.

Example 3 Swatches of impregnated sateen containing 24.8%polyethylacrylate (Hycar 4501) were briefly treated in separate portionsof perfluorooctanoic acid chromi-nuclear complex solution containing0.4% solid complex and suflicient 10% HMTA to give a series of solutionsranging in pH from 2.8 to 5.0. After processing of the treated sateen asdescribed in Example 1, it was found that the time required forpenetration by liquid stabilized GB increased from 2400 seconds for thefabrics treated at pH 2.8 to 6,550 seconds for the fabric treated at pHof 5.0. The wetting times also increased with increasing pH of thechrome complex treating solution from 18,000 seconds at pH 2.8 to 24,000seconds at pH 5 .0.

Example 4 A series of swatches of unscoured sateen were impregnated inaqueous dispersions of polyethyl acrylate ranging in total solidsconcentration from 50 to 5%. After padding to remove excess emulsion andair drying, the impregnated swatches had dry pick-ups ranging from 5.9%to 47.1%. It was found that the original air permeability of theuntreated sateen, 12.8 cu. ft./ min./ sq. ft.,

was increased to a maximum value of 21.0 at 29.2% pickup. Theimpregnated swatches having 5.9 to 47.1% dry pick-up were brieflyimmersed in a perfluorooctanoic chromi-nuclear complex solution, havinga temperature of 5 0., containing 0.4% solid complex and sufficient 10%hexamethylene tetramine to increase the pH to 5.0. After treatment theswatches were processed as described in Example 1. The effect ofvariation in polyethyl ac rylate pick-up was evaluated from wettingtests with stabihzed liquid GB. The results are summarized in the tablebelow:

Penetration Wetting Dry Pick-Up of Pretreating Polymer Time, Time,

Seconds Seconds The original high air permeability of the impregnatedsateen is reduced somewhat by treatment with the chrominuclear complexsolution and subsequent processing. However, the air permeability of thefinal treated sateen is at least as high as that of the originaluntreated fabric (12.8 cu. ft./min./sq. ft).

Example 5 Unscoured sateen was treated exactly as in Example 1 exceptthat a commercially available polyvinylacetate dispersion (Rhoplex WN75)was employed for the initial impregnation of the sateen and that theair-dry impregnated sateen Was not washed prior to application of thechromi-nuclear complex solution. With a polymer pickup of 37.2% thefinal treated sateen resisted the penetration of liquid stabilized GBfor 300 seconds, and resisted complete wetting for 9500 seconds.

Example 6 Unscoured sateen was treated exactly as in Example 1 exceptthat a laboratory-prepared polymethyl acrylate dispersion was employedfor the initial impregnation. The unscoured sateen was impregnated in a33% dispersion of this polymer and allowed to air dry giving a slightlystiff fabric having 38% dry pick-up. After treatment with aqueouschromi-nuclear complex solution and processing as described in Example1, the repellency was evaluated with stabilized liquid GB; penetrationtime 4500 seconds, wetting time 7600 seconds.

Example 7 Unscoured sateen was treated exactly as in Example No. 1except that a commercially available acrylonitrilebutadiene copolymeremulsion, Hycar 1552, was employed for the initial impregnation. Thesateen was impregnated in a 35% aqueous dispersion of the copolymer andallowed to air dry giving a very slightly stiff fabric having a drypick-up of 40.4%. After treatment with a 1.5% solution of thechromi-nuclear perfluoro octanoic acid complex at a pH of 4.8, thesateen was processed as described in Example N0. 1. The treated sateenresisted penetration by liquid GB for 1300 seconds, and resistedcomplete wetting for at least 10,000 seconds.

Example 8 Unscoured sateen was treated exactly as in Example 1 exceptthat a 9.7% solution of polyethyl acrylate (Hycar 4501) in acetone wasemployed for the initial impregnation. The air-dried fabric containing25.1% dry polymer was treated in a 0.4% chromi-nuclear complex solutionat pH of 5.0 and a temperature of 5 C. After processing as in Example 1,the repellency was evaluated with stabilized liquid GB; penetrationtime, 2500 seconds; Wetting time, 75 seconds.

We claim: 7 V

1. A process of rendering a textile material highly resistant to wettingand penetration by liquid chemical Warfare agents, comprising:impregnating the textile with an inert volatile liquid containing apolymer selected from the group consisting of polymethyl acrylate,polyethyl acrylate, polyvinyl acetate, and copolymers of acrylonitrileand butadiene containing from about 30 to 60 weight per cent ofacrylonitrile, to a dry pick-up of from about 25 to 50 weight percent;air drying the impregnated textile at a temperature of from about 20 to30 centigrade; immersing the dry impregnated textile in andsubstantially imme diately removing it from contact with a liquidcomposi tion, which is maintained at a temperature between its freezingpoint and about C., and which consists essentially of: wtaer, from about0.4 to 3.3 weight percent of a water soluble alkanol, from about 0.2 to1.5 weight percent of a Werner-type chrominuclear complex in which theacido groups consist essentially of perfluoroalkanoyl groups containingfrom about 6 to 18 carbon atoms, and sufiicient water solublenitrogen-base to produce a pH of from about 4.8 to 5.5; substantiallyimmediately freeing the Wet textile of drops of the liquid; and dryingthe wet textile at a temperature of from about 90 to 110 C. for fromabout to 90 minutes.

2. The process of claim 1 in which the polymer with which the textile isimpregnated is polyethyl acrylate.

3. The process of claim 1 in which the polymer with which the textile isimpregnated is polyvinyl acetate.

4. The process of claim 1 in which the polymer with which the textile isimpregnated is polymethyl acrylate.

5. The process of claim 1 in which the polymer with which the textile isimpregnated is a copolymer of acrylonitrile and butadiene containingfrom about 30 to by weight acrylonitrile.

References Cited in the file of this patent UNITED STATES PATENTS2,552,910 Steinman May 15, 1951 2,611,718 Steinman Sept. 23, 19522,693,458 Olson Nov. 2, 1954 2,744,835 Caroselli May 8, 1956 2,745,770Kingerley May 15, 1956

1. A PROCESS OF RENDERING A TEXTILE MATERIAL HGIHLY RESISTANT TO WETTINGAND PENETRATION BY LIQUID CHEMICAL WARFARE AGENTS, COMPRISING:IMPREGNATING THE TEXTILE WITH AN INERT VOLATILE LIQUID CONTAININGAPOLYMER SELECTED FROM THE GROUP CONSISTING OF POLYMETHYL ACRYLATE,POLYETHYL ACRYLATE, POLYVINYL ACETATE, AND COPOLYMERSO ACRYLONITRILE ANDBUTADIENE CONTAINING FROM ABOUT 30 TO 60 WEIGHT PERCENT OFACRYLONITRILE, TO A DRY PICK-UP OF FROM ABOUT 25 TO 50 WEIGHT PERCENT;AIR DRYING THE IMPREGNATED TEXTILE AT A TEMPERATURE OF FROM ABOUT 20 TO30* CENTIGRADE; IMMERSING THE DRY IMPREGNATED TEXTILE IN ANDSUBSTANTIALLY IMMEDIATELY REMOVING IT FROM CONTACT WITH A LIQUIDCOMPOSITION, WHICH IS MAINTAINED AT A TEMPRATURE BETWEEN ITS FREEZINGPOINT AND ABOUT 5* C., AND WHICH CONSISTS ESSENTIALLY OF: WATER, FROMABOUT 0.4 TO 3.3 WEIGHT PERCENT OF A WATER SOLUBLE ALKANOL, FROM ABOUT0.2 TO 1.5 WEIGHT PERCENT OF A WERNER-TYPE CHROMINUCLEAR COMPLEX INWHICH THE ACIDO GROUPS CONSIST ESSENTIALLY OF PERFLUOROALKANOYL GROUPSCONTAINING FROM ABOUT 6 TO 18 CARBON ATOMS, AND SUFFICIENT WATER SOLUBLENITROGEN-BASE TO PRODUCE A PH OF FROM ABOUT 4.8 TO 5.5; SUBSTANTIALLYIMMEDIATELY FREEING THE WET TEXTILE OF DROPS OF THE LIQUID; AND DRYINGTHE WET TEXTILE AT A TEMPERATURE OF FROM ABOUT 90 TO 110*C. FOR FROMABOUT 30 TO 90 MINUTES.